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Role of the carboxy‐termini of tubulin on its chaperone‐like activity
Author(s) -
Sarkar Taradas,
Manna Tapas,
Bhattacharyya Shankar,
Mahapatra Pradip,
Poddar Asim,
Roy Siddhartha,
Pena Jose,
Solana Rafael,
Tarazona Raquel,
Bhattacharyya Bhabatarak
Publication year - 2001
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.1091
Subject(s) - chaperone (clinical) , subtilisin , biochemistry , protein subunit , peptide , tubulin , c terminus , chaperonin , peptide sequence , biology , n terminus , chemistry , protein folding , enzyme , microbiology and biotechnology , amino acid , microtubule , medicine , pathology , gene
Abstract Mutational analysis and the enzymatic digestion of many chaperones indicate the importance of both hydrophobic and hydrophilic residues for their unique property. Thus, the chaperone activity of α‐crystallin is lost due to the substitution of hydrophobic residues or upon enzymatic digestion of the negatively charged residues. Tubulin, an eukaryotic cytoskeletal protein, exhibits chaperone‐like activity as demonstrated by prevention of DTT‐induced aggregation of insulin, thermal aggregation of alcohol dehydrogenase, βγ‐crystallin, and other proteins. We have shown that the tubulin lost its chaperone‐like activity upon digestion of its negatively charged C‐termini. In this article, the role of the C‐terminus of individual subunits has been investigated. We observe that the digestion of C‐terminus of β‐subunit with subtilisin causes loss of chaperone‐like activity of tubulin. The contribution of C‐terminus of α‐subunit is difficult to establish directly as subtilisin cleaves C‐terminus of β‐subunit first. This has been ascertained indirectly using a 14‐residue peptide P2 having the sequence corresponding to a conserved region of MHC class I molecules and that binds tightly to the C‐terminus of α‐subunit. We have shown that the binding of P2 peptide to αβ‐tubulin causes complete loss of its chaperone‐like activity. NMR and gel‐electrophoresis studies indicate that the P2 peptide has a significant higher binding affinity for the C‐terminus of α‐subunit compared to that of β‐subunit. Thus, we conclude that both the C‐termini are necessary for the chaperone‐like activity of tubulin. Implications for the chaperone functions in vivo have been discussed. Proteins 2001;44:262–269. © 2001 Wiley‐Liss, Inc.